The present invention relates to a device and a method for determining the value of a binary item, delivered in a redundant manner, and representative of a parameter of a system.
When there is a desire to determine the value of a binary item representative of a parameter of a system, for example the “pressed” or “released” position of a pedal, it is possible to use a determination element such as a measurement sensor of the “on/off” type which indicates the state of the system.
The binary item then represents the state of the system. In such a case, a failure of this sensor or of the data acquisition subsystem for this sensor can cause any binary item to be lost or erroneous binary item to be delivered.
The addition of a second, independent, determination element, for example a second similar sensor, provides a way of ensuring that, should one determination element fail, a correct binary item will still be transmitted by the second determination element.
However, when the two binary items respectively transmitted by the two determination elements are contradictory, there is no way of knowing which one is correct. This can occur, for example, when one of the determination elements is malfunctioning and transmitting a constant binary item.
The addition of a third determination means, for example a third sensor, would eliminate this contradiction. However, the addition of a third determination element is excessively costly compared to a solution with two determination elements.
There are systems managing the redundancy of a binary item transmitted by two determination elements.
The document U.S. Pat. No. 5,016,587 uses a time correlation with which to detect the inconsistencies and identify the defective sensor after using complex and costly processing operations.